Recovery of the ovine fetus from sustained hypoxia: effects on endocrine, cardiovascular, and biophysical activity.

Objective: The purpose of this study was (1) to determine the ability of the ovine fetus to recover from a self-limiting asphyxial insult and (2) to monitor cardiovascular and biophysical activity as potential markers of such an insult or underlying neurologic impairment.

Study Design: Nineteen fetal sheep were studied (12 hypoxia and 7 control) at 0.9 of gestation during a 24-hour control period, up to 8 hours of either sustained hypoxemia or room air, and for a 40-hour recovery period. Fetal heart rate, blood pressure, electrocortical activity, electroocular activity, and breathing movements were monitored continuously. Fetal arterial blood was sampled at set times for blood gases, pH, lactate, and catecholamine levels.

Result: Induced fetal hypoxemia resulted in a lactic metabolic acidosis that progressively worsened, with death occurring in three of the animals during the early recovery period. The remaining animals showed a rapid metabolic and endocrine normalization of values by 24 hours. Fetal cardiovascular and biophysical measurements likewise returned to control values during the early recovery period, although three animals had seizure-like activity.

Conclusion: The near-term ovine fetus surviving a sustained asphyxial insult sufficient to induce neuropathologic change within the brain demonstrates a normalization of biophysical activity during the early period of recovery, although seizure-like activity may subsequently be evident.